Optical module comprising lens assembly

ABSTRACT

In one example, an apparatus comprises: a lens assembly comprising one or more polymer layers, each layer including a lens portion and an extension portion and an image sensor positioned below the lens assembly and bonded to the lens assembly via a bonding layer and configured to sense light that passes through the lens portion of the one or more polymer layers.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/927,415, filed on Jul. 13, 2020, and titled OPTICAL MODULE COMPRISINGLENS ASSEMBLY, which claims priority to U.S. Provisional Application No.62/874,452, filed on Jul. 15, 2019 and titled OPTICAL MODULE COMPRISINGLENS ASSEMBLY, and U.S. Provisional Application No. 63/036,858, filedJun. 9, 2020 and titled OPTICAL MODULE COMPRISING LENS ASSEMBLY, whichare assigned to the assignee hereof and are incorporated herein byreference in their entirety for all purposes.

BACKGROUND

The disclosure relates generally to an optical module, and morespecifically to an optical module comprising one or more lenses.

An optical module can include, for example, an image sensor module, alight projector module, etc. An image sensor module typically includesan image sensor, which can include one or more image sensor chips, andone or more lenses. The one or more lenses can gather incident light andfocus the light towards a light receiving surface of the image sensor.The image sensor includes light sensing elements (e.g., photodiodes)that can receive the incident light that passes through the one or morelenses via the light receiving surface, and convert the received lightto electrical signals. The electrical signals can represent, forexample, intensities of light from a scene. Based on the electricalsignals, an image processor can generate an image of the scene. On theother hand, a light projector module may include a light source and oneor more lens. The light source can emit light, which can pass throughthe lens and propagate to a far field. The assembly of the one or morelenses with the image sensor/light source can affect various propertiesof the optical module.

SUMMARY

The disclosure relates generally to an optical module, and morespecifically to an optical module comprising one or more lenses.

In one example, an apparatus is provided. The apparatus comprises: alens assembly comprising one or more polymer layers, each layerincluding a lens portion and an extension portion; and an image sensorbelow the lens assembly and bonded to the lens assembly via a bondinglayer and configured to sense light that passes through the lens portionof the one or more polymer layers.

In some aspects, each of the one or more polymer layers is made of acyclic olefin copolymer (COC) material.

In some aspects, each of the one or more polymer layers is made of atleast one of: a polycarbonate material, or a polyester material.

In some aspects, each of the one or more polymer layers is made from oneor more injection molding processes.

In some aspects, a footprint of the lens assembly is substantiallyidentical to a footprint of the image sensor.

In some aspects, the bonding layer is distributed around a perimeter ofthe image sensor to surround a light receiving surface of the imagesensor facing the lens portions of the one or more polymer layers.

In some aspects, the lens assembly further comprises a light outputtingsurface. The bonding layer is distributed over a light receiving surfaceof the image sensor to bond the light receiving surface of the imagesensor with the light outputting surface of the lens assembly.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The extension portion of a pair of polymer layers of theplurality of polymer layers are bonded via an adhesive.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The lens assembly further includes a plurality ofspacers comprising a first spacer, the first spacer being sandwichedbetween the extension portion of a pair of polymer layers of theplurality of polymer layers.

In some aspects, the first spacer is bonded to the extension portion ofthe pair of polymer layers.

In some aspects, the plurality of spacers are made of an opaque materialcomprising one of: a polymer, or a metal.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The lens portion of a pair of polymer layers of theplurality of polymer layers are bonded via an adhesive.

In some aspects, the apparatus further comprises an opaque coating onexterior surfaces of the lens assembly, wherein the exterior surfaces donot face the image sensor.

In some aspects, the apparatus further comprises an opaque lens holderto hold the one or more polymer layers. The opaque lens holder comprisesa housing and a retainer. The housing is configured to hold the one ormore polymer layers. The retainer is configured to retain the one ormore polymer layers within the housing. The image sensor is bonded toeither the housing or the retainer.

In some aspects, at least a part of the retainer is sandwiched betweenthe housing and the image sensor.

In some aspects, the housing includes a first bottom surface surroundinga bottom opening of the housing facing the retainer and bonded with atop surface of the retainer via a first adhesive.

In some aspects, the retainer includes a middle surface to mount aefilter, and a second bottom surface to bond with the image sensor via asecond adhesive.

In some aspects, the first bottom surface of the housing comprises afirst uneven surface. The top surface of the retainer comprises a seconduneven surface. The first uneven surface and the second uneven surfaceare complimentary to each other and are bonded with each other via thefirst adhesive.

In some aspects, the housing comprises a barrel and a base portion. Thebase portion includes the first uneven surface to bond with the seconduneven surface of the retainer.

In some aspects, the housing and the retainer are made of a polymermaterial using an injection molding process.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative examples are described with reference to the followingfigures.

FIG. 1A, FIG. 1B, and FIG. 1C are diagrams of an example of a near-eyedisplay.

FIG. 2 is an example of a cross section of the near-eye display.

FIG. 3 illustrates an isometric view of an example of a waveguidedisplay with a single source assembly.

FIG. 4 illustrates a cross section of an example of the waveguidedisplay.

FIG. 5 is a block diagram of an example of a system including thenear-eye display.

FIG. 6A and FIG. 6B illustrates examples of an image sensor module andits operations.

FIG. 7 illustrates other examples of an image sensor module.

FIG. 8A, FIG. 8B, and FIG. 8C illustrates other examples of an imagesensor module and its fabrication.

FIG. 9A, FIG. 9B, and FIG. 9C illustrate other examples of an imagesensor module.

FIG. 10 illustrates another example of an image sensor module.

FIG. 11A, FIG. 11B, and FIG. 11C illustrate other examples of an imagesensor module.

FIG. 12A, FIG. 12B, and FIG. 12C illustrate other examples of an imagesensor module.

FIG. 13A and FIG. 13B illustrate examples of an image sensor module.

FIG. 14A, FIG. 14B, FIG. 14C, and FIG. 14D illustrate a method offorming an image sensor on a printed circuit board (PCB).

The figures depict examples of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative examples of the structuresand methods illustrated may be employed without departing from theprinciples, or benefits touted, of this disclosure.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, specificdetails are set forth in order to provide a thorough understanding ofcertain inventive examples. However, it will be apparent that variousexamples may be practiced without these specific details. The figuresand description are not intended to be restrictive.

An optical module can include, for example, an image sensor module, alight projector module, etc. An image sensor module typically includesan image sensor and one or more lenses. The one or more lenses cangather incident light and focus the light towards a light receivingsurface of the image sensor. The image sensor can include an array ofpixel cells to generate electrical signals representing a distributionof light intensities received by the image sensor. Based on theelectrical signals, an image processor can generate an image of thescene. The image sensor module can be soldered onto a printed circuitboard (PCB) which also includes an image processor. The PCB includeelectrical traces to transmit the electrical signals from the imagesensor module to the image sensor, which can generate an image of thescene based on the electrical signals. On the other hand, a lightprojector module may include a light source and one or more lens. Thelight source can be soldered onto a PCB and controlled by electricalsignals from the PCB to emit light. The light can pass through the lensto become, for example, collimated light beams.

The physical properties of the lens of the optical module can determinethe optical properties as well as the performance of the optical module.Specifically, the curvature and refractive index of the lens candetermine the focal length of the lens, which can define the field ofview of the image sensor module. The field of view, in turn, candetermine an area of the scene to be captured by the image sensormodule. Moreover, the Abbe number of the lens can determine thevariation of refractive index versus wavelength. Further, thebirefringence of the lens can determine the variation of the refractiveindex of the lens with respect to the polarization and propagationdirection of the incident light. Both Abbe number and birefringence cancontrol the dispersion of light by the lens and can be determined by thematerial of the lens. All these optical properties can affect thequality of an image (e.g., amount of information captured, blurriness,distortion) captured by the image sensor module, the dispersion of lightproduced by the light projector module, etc.

The assembly of the one or more lenses and the image sensor in the imagesensor module can also affect the optical properties as well as theperformance of the image sensor module. Specifically, the alignment ofthe image sensor with respect to the lens (e.g., relative orientations,positions) can also affect the reception of the light by the imagesensor. For example, the light receiving surface of the image sensorneeds to be at the focal point of the lens, and be perpendicular withthe optical axis, so that different points of the light receivingsurface can receive the focused light to enable the image sensor to havethe field of view defined by the focal length of the one or more lenses.But if the light receiving surface of the image sensor is not at thefocal point of the one or more lenses and/or not perpendicular to theoptical axis, at least some locations of the light receiving surface mayreceive divergent/dispersed incident light, and the resulting image maybecome blurred and distorted. The performance of the light projectormodule can also be affected in a similar way by the alignment betweenthe light source and the lens.

Moreover, the assembly of the lens with the image sensor in the imagesensor module can also affect the footprint of the image sensor module.For example, a housing may be used to hold the lens and the image sensortogether at their respective aligned positions and orientations. But ifthe housing surrounds the image sensor, the housing can add to thefootprint of the image sensor module such that the image sensor moduleoccupies a larger area on the PCB than the image sensor. The increasedfootprint can be undesirable especially for integrating the image sensorin a mobile device, such as a wearable device, a smart glass, etc.,where space is very limited. The same is true for integrating a lightprojector in a mobile device.

This disclosure relates to an image sensor module that can provideimproved optical properties as well as reduced form factor, as well as amethod of fabricating the image sensor module. The image sensor moduleincludes a lens assembly including one or more lenses, and an imagesensor. Each of the plurality of lens can be held by a housing, whichcan be in the form of a barrel. The lenses can be separated by spacersto form a lens stack. The entire lens stack (including the housing, thespacers, etc.) can be positioned on the image sensor, with the lensholder and/or spacers defining the position of each lens in the lensstack with respect to the light receiving surface of the image sensor.The lens holder and the spacers can provide mechanical support andrigidity to prevent the deformation of lens stack, which can degrade theoverall optical properties of the image sensor module, while not addingto the footprint of the image sensor module. The lens assembly can bebonded to a light receiving surface of the image sensor via a layer ofadhesive, whereas the image sensor can be soldered onto a PCB. The lightreceiving surface can be on a glass substrate placed on the imagesensor. As the entirety of the lens assembly is positioned on the imagesensor, the footprint of the image sensor module (on the PCB) can bereduced to become substantially identical to the footprint of the imagesensor.

In some examples, the one or more lenses of the lens assembly can bemade of a polymer material (e.g., Cyclo Olefin Polymer) and can befabricated using high precision processes such as injection molding. Thehigh precision fabrication of the one or more lenses provide improvedcontrol of the physical properties (e.g., curvature, shape, size, etc.)of the lens, whereas the polymer material can reduce the Abbe number andthe birefringence of the lens, both of which can provide improvedcontrol of the optical properties of the lens and the overallperformance of the image sensor module.

In some examples, the optical elements of an image sensor module mayinclude, in addition to the lenses stack, a filter. The filter caninclude a filter array to select different frequency components of thelight to be detected by the image sensor, or a single frequencycomponent of the light to be detected by all pixel cells. The imagesensor includes light sensing elements (e.g., photodiodes) that canreceive the different frequency components of the light selected by thefilter array via the light receiving surface, and convert the frequencycomponents to electrical signals. The electrical signals can represent,for example, intensities of the different frequency components of lightfrom a scene. Moreover, the filter array can also be part of a projectorto select the frequency range of output light, such as an infraredfrequency range.

In a case where the image sensor module includes a filter, the imagesensor module may include, in additional to the housing, a retainer.Both the housing and the retainer can be made of, for example, apolycarbonate (PC) material, a polymer material (e.g., liquid crystalpolymer, LCP) using an injection molding process, etc., and can togetherform a holder structure. The filter can be mounted in the retainer,while the retainer can be mounted within the housing between the lensesstack and a bottom opening of the housing. Within the housing, theretainer can be positioned away from the bottom opening so that theretainer does not protrude out of the bottom opening. Moreover, theretainer is also pushed against the lenses stack. Such arrangements canprovide additional physical support to the lenses stack and prevent thelenses stack from falling out of the bottom opening. A bottom surface ofthe housing around the bottom opening can be bonded (e.g., via anadhesive followed by ultraviolet light curing) onto the light receivingsurface of the image sensor, to set the alignments and orientations ofthe lenses and the filter with respect to the image sensor. Light canthen enter the housing via the top opening and become focused by thelenses stack and filtered by the filter. The filtered light can thenexit out of the bottom opening and enter the image sensor.

With examples of the present disclosure, the footprint of the imagesensor module can be reduced as the entirety of the lens assembly can bepositioned on the image sensor. Moreover, the optical properties of theimage sensor module can be improved by, for example, including lens thatare fabricated using a high precision process (e.g., injection molding)and using materials that provide low birefringence and Abbe numbers. Thealignment of the lens with respect to the image sensor can also beimproved by the alignment process involving the light sensor operationby the image sensor as the data generated by the image sensor canprovide an accurate account of the degree of alignment between the imagesensor and the lens assembly.

Although the above arrangements can shrink the footprint of the imagesensor module, the mounting of the retainer within the housing cancreate various issues which can affect the assembly of the image sensormodule as well as the optical properties and performance of the imagesensor module. Specifically, the bottom surface of the housing providesa very limited area for applying the adhesive, which makes the bondingof the housing to the image sensor difficult. Specifically, the bottomopening can be enlarged to allows more pixel cells to receive lightthrough the lenses and filter, which can improve the imaging resolution.But the bottom surface of the housing, which surrounds the bottomopening and the retainer, adds to the footprint and may need to beshrunk to reduce the footprint of the image sensor module. As a result,the available area for applying the adhesive can be reduced. The reducedbonding area can lead to weaker bonding between the housing and theimage sensor. Moreover, due to the reduced bonding area, the amount ofadhesive applied, as well as the locations where the adhesive isapplied, need to be controlled with very high precision. This is toprevent the adhesive applied to the bottom surface of the housing fromspilling into the bottom opening when the housing and the image sensorare brought together. But the requisite precision may becomeunachievable as the footprint of the image sensor module continues toshrink. The weaker bonding between the housing and the image sensor canintroduce variations in the alignments and orientations of the lensesand the filter with respect to the image sensor. Moreover, the adhesivespilled into the bottom opening can obfuscate the filter and/or thepixel cells of the image sensor. All these can degrade the light sensingperformance of the image sensor module. In addition, by mounting theretainer within the housing, the bottom surface of the housing and thesurface of the retainer add up and increases the footprint of the imagesensor module.

In some examples, to further reduce the footprint of the image sensorand to further improve the bonding between the housing and image sensor,the retainer is mounted on a bottom surface of the housing at a bottomopening of the housing, and sandwiched between the housing and the imagesensor, such that the housing, the retainer, and the image sensor formsa stack. The retainer includes a first surface to bond with the bottomsurface of the housing. The first surface is also stacked against thelenses stack to provide additional physical support to the lenses, andto prevent the lenses stack from falling out of the bottom opening. Theretainer further includes a second surface opposite from the firstsurface. The second surface can be bonded to the light receiving surfaceof the image sensor via, for example, an adhesive.

With the disclosed techniques in which the housing, the retainer, andthe image sensor form a stack. Such arrangements can reduce the surfacearea surrounding the filter and the footprint of the image sensormodule. Moreover, the retainer surface can be made larger to provide alarger area for applying the adhesive for bonding with the image sensor,which can improve the bonding between the retainer and the image sensorand relax the precision requirements for application of adhesive. As theretainer does not surround the lenses stack, unlike the housing, theretainer surface can be increased without a corresponding increase inthe footprint of the image sensor module. As a result, the footprint ofthe image sensor module can be reduced, while the bonding between theimage sensor and the holder structure (including the housing and theretainer) can be improved to provide improve control of the alignmentsand orientations of the lenses and the filter with respect to the imagesensor. All of these can further reduce the footprint and improve theperformance of the image sensor module.

The image sensor can be bonded to the lens assembly, which may includethe housing, the lenses stack, the filter, etc., via a layer ofadhesive. The image sensor can be bonded to the housing directly, or tothe retainer of the filter, of the lens assembly. Prior to the bonding,the image sensor can be soldered onto the PCB via a reflow process whichtypically occurs at a high temperature, to prevent the reflow processfrom deforming the lens in the lens assembly. During the fabrication ofthe image sensor module, the adhesive can be applied on the lensassembly and/or the image sensor, and the image sensor can be attachedto the lens assembly via the adhesive to form the bonding. While theadhesive is still in a liquid state, an alignment process involving anlight sensing operation by the image sensor can be performed to adjustthe position and/or orientation of the image sensor with respect to thelens assembly. In the alignment process, light can be projected to thelens assembly, and the image sensor can be operated to generate sensordata based on the light that passes through the lens assembly. Thesensor data can reflect a degree of alignment (e.g., based on ameasurement of blurriness, distortion) between the lens assembly and theimage sensor. The position and/or orientation of the image sensor can beadjusted until, for example, a target alignment is achieved. The imagesensor can then be fixed at its aligned position/orientation based oncuring the adhesive to harden the adhesive. The adhesive can be curedby, for example, ultraviolet light, a thermal process at a temperaturelower than the melting point of the one or more lenses, etc., such thatthe curing process also does not deform the lens. The techniquesdescribed above can also be used to form a light projector system withreduced footprint and improved performance.

The disclosed techniques may include or be implemented in conjunctionwith an artificial reality system. Artificial reality is a form ofreality that has been adjusted in some manner before presentation to auser, which may include, e.g., a virtual reality (VR), an augmentedreality (AR), a mixed reality (MR), a hybrid reality, or somecombination and/or derivatives thereof. Artificial reality content mayinclude completely generated content or generated content combined withcaptured (e.g., real-world) content. The artificial reality content mayinclude video, audio, haptic feedback, or some combination thereof, anyof which may be presented in a single channel or in multiple channels(such as stereo video that produces a three-dimensional effect to theviewer). Additionally, in some examples, artificial reality may also beassociated with applications, products, accessories, services, or somecombination thereof, that are used to, for example, create content in anartificial reality and/or are otherwise used in (e.g., performactivities in) an artificial reality. The artificial reality system thatprovides the artificial reality content may be implemented on variousplatforms, including a head-mounted display (HMD) connected to a hostcomputer system, a standalone HMD, a mobile device or computing system,or any other hardware platform capable of providing artificial realitycontent to one or more viewers.

FIG. 1A is a diagram of an example of a near-eye display 100. Near-eyedisplay 100 presents media to a user. Examples of media presented bynear-eye display 100 include one or more images, video, and/or audio. Insome examples, audio is presented via an external device (e.g., speakersand/or headphones) that receives audio information from the near-eyedisplay 100, a console, or both, and presents audio data based on theaudio information. Near-eye display 100 is generally configured tooperate as a virtual reality (VR) display. In some examples, near-eyedisplay 100 is modified to operate as an augmented reality (AR) displayand/or a mixed reality (MR) display.

Near-eye display 100 includes a frame 105 and a display 110. Frame 105is coupled to one or more optical elements. Display 110 is configuredfor the user to see content presented by near-eye display 100. In someexamples, display 110 comprises a waveguide display assembly fordirecting light from one or more images to an eye of the user.

Near-eye display 100 further includes image sensor modules 120 a, 120 b,120 c, and 120 d. Each of image sensor modules 120 a, 120 b, 120 c, and120 d may include a pixel array configured to generate image datarepresenting different fields of views along different directions. Forexample, sensor modules 120 a and 120 b may be configured to provideimage data representing two fields of view towards a direction A alongthe Z axis, whereas sensor 120 c may be configured to provide image datarepresenting a field of view towards a direction B along the X axis, andsensor 120 d may be configured to provide image data representing afield of view towards a direction C along the X axis.

In some examples, sensor modules 120 a-120 d can be configured as inputdevices to control or influence the display content of the near-eyedisplay 100, to provide an interactive VR/AR/MR experience to a user whowears near-eye display 100. For example, sensor modules 120 a-120 d cangenerate physical image data of a physical environment in which the useris located. The physical image data can be provided to a locationtracking system to track a location and/or a path of movement of theuser in the physical environment. A system can then update the imagedata provided to display 110 based on, for example, the location andorientation of the user, to provide the interactive experience. In someexamples, the location tracking system may operate a simultaneouslocalization and mapping algorithm to track a set of objects in thephysical environment and within a view of field of the user as the usermoves within the physical environment. The location tracking system canconstruct and update a map of the physical environment based on the setof objects, and track the location of the user within the map. Byproviding image data corresponding to multiple fields of views, sensormodules 120 a-120 d can provide the location tracking system a moreholistic view of the physical environment, which can lead to moreobjects to be included in the construction and updating of the map. Withsuch an arrangement, the accuracy and robustness of tracking a locationof the user within the physical environment can be improved.

In some examples, near-eye display 100 may further include one or moreactive illuminators 130 to project light into the physical environment.The light projected can be associated with different frequency spectrums(e.g., visible light, infrared light, ultraviolet light, etc.), and canserve various purposes. For example, illuminator 130 may project lightin a dark environment (or in an environment with low intensity ofinfrared light, ultraviolet light, etc.) to assist sensor modules 120a-120 d in capturing images of different objects within the darkenvironment to, for example, enable location tracking of the user.Illuminator 130 may project certain markers onto the objects within theenvironment, to assist the location tracking system in identifying theobjects for map construction/updating.

In some examples, illuminator 130 may also enable stereoscopic imaging.For example, one or more of sensor modules 120 a or 120 b can includeboth a first pixel array for visible light sensing and a second pixelarray for infrared (IR) light sensing. The first pixel array can beoverlaid with a color filter (e.g., a Bayer filter), with each pixel ofthe first pixel array being configured to measure intensity of lightassociated with a particular color (e.g., one of red, green or bluecolors). The second pixel array (for IR light sensing) can also beoverlaid with a filter that allows only IR light through, with eachpixel of the second pixel array being configured to measure intensity ofIR lights. The pixel arrays can generate a red-green-blue (RGB) imageand an IR image of an object, with each pixel of the IR image beingmapped to each pixel of the RGB image. Illuminator 130 may project a setof IR markers on the object, the images of which can be captured by theIR pixel array. Based on a distribution of the IR markers of the objectas shown in the image, the system can estimate a distance of differentparts of the object from the IR pixel array, and generate a stereoscopicimage of the object based on the distances. Based on the stereoscopicimage of the object, the system can determine, for example, a relativeposition of the object with respect to the user, and can update theimage data provided to display 100 based on the relative positioninformation to provide the interactive experience.

As discussed above, near-eye display 100 may be operated in environmentsassociated with a very wide range of light intensities. For example,near-eye display 100 may be operated in an indoor environment or in anoutdoor environment, and/or at different times of the day. Near-eyedisplay 100 may also operate with or without active illuminator 130being turned on. As a result, image sensor modules 120 a-120 d may needto have a wide dynamic range to be able to operate properly (e.g., togenerate an output that correlates with the intensity of incident light)across a very wide range of light intensities associated with differentoperating environments for near-eye display 100.

FIG. 1B is a diagram of another example of near-eye display 100. FIG. 1Billustrates a side of near-eye display 100 that faces the eyeball(s) 135of the user who wears near-eye display 100. As shown in FIG. 1B,near-eye display 100 may further include a plurality of illuminators 140a, 140 b, 140 c, 140 d, 140 e, and 140 f. Near-eye display 100 furtherincludes a plurality of image sensor modules 150 a and 150 b.Illuminators 140 a, 140 b, and 140 c may emit lights of certainfrequency range (e.g., near infrared range (NIR)) towards direction D(which is opposite to direction A of FIG. 1A). The emitted light may beassociated with a certain pattern, and can be reflected by the lefteyeball of the user. Sensor module 150 a may include a pixel array toreceive the reflected light and generate an image of the reflectedpattern. Similarly, illuminators 140 d, 140 e, and 140 f may emit NIRlights carrying the pattern. The NIR lights can be reflected by theright eyeball of the user, and may be received by sensor module 150 b.Sensor module 150 b may also include a pixel array to generate an imageof the reflected pattern. Based on the images of the reflected patternfrom sensor modules 150 a and 150 b, the system can determine a gazepoint of the user, and update the image data provided to display 100based on the determined gaze point to provide an interactive experienceto the user.

As discussed above, to avoid damaging the eyeballs of the user,illuminators 140 a, 140 b, 140 c, 140 d, 140 e, and 140 f are typicallyconfigured to output lights of very low intensities. In a case whereimage sensor modules 150 a and 150 b comprise the same sensor devices asimage sensor modules 120 a-120 d of FIG. 1A, the image sensor modules120 a-120 d may need to be able to generate an output that correlateswith the intensity of incident light when the intensity of the incidentlight is very low, which may further increase the dynamic rangerequirement of the image sensor modules.

Moreover, the image sensor modules 120 a-120 d may need to be able togenerate an output at a high speed to track the movements of theeyeballs. For example, a user's eyeball can perform a very rapidmovement (e.g., a saccade movement) in which there can be a quick jumpfrom one eyeball position to another. To track the rapid movement of theuser's eyeball, image sensor modules 120 a-120 d need to generate imagesof the eyeball at high speed. For example, the rate at which the imagesensor modules generate an image frame (the frame rate) needs to atleast match the speed of movement of the eyeball. The high frame raterequires short total exposure time for all of the pixel cells involvedin generating the image frame, as well as high speed for converting thesensor outputs into digital values for image generation. Moreover, asdiscussed above, the image sensor modules also need to be able tooperate at an environment with low light intensity.

FIG. 1C illustrates a close-up view of near-eye display 100. As shown inFIG. 1C, frame 105 may house image sensor module 120 a and illuminator130. Image sensor module 120 a and illuminator 130 may be connected to aprinted circuit board (PCB) which provides electrical connectionsbetween different subsystems of near-eye display 100. The footprint ofimage sensor module 120 a (e.g., along the x and y axes) on PCB 160, aswell as other subsystems connected to PCB 160 can determine a thickness(labelled “t” in FIG. 1C) of frame 105 needed to house PCB 160. It maybe desirable to reduce the thickness of frame 105 to reduce the weightof frame 105, to increase the area of display 110, and to improveaesthetics, all of which can improve the user experience. To reduce thethickness of frame 105, the footprints of the sub-systems on PCB 160,such as image sensor module 120 a, illuminator 130, etc., may need to bereduced.

FIG. 2 is an example of a cross section 200 of near-eye display 100illustrated in FIG. 1. Display 110 includes at least one waveguidedisplay assembly 210. An exit pupil 230 is a location where a singleeyeball 220 of the user is positioned in an eyebox region when the userwears the near-eye display 100. For purposes of illustration, FIG. 2shows the cross section 200 associated eyeball 220 and a singlewaveguide display assembly 210, but a second waveguide display is usedfor a second eye of a user.

Waveguide display assembly 210 is configured to direct image light to aneyebox located at exit pupil 230 and to eyeball 220. Waveguide displayassembly 210 may be composed of one or more materials (e.g., plastic,glass, etc.) with one or more refractive indices. In some examples,near-eye display 100 includes one or more optical elements betweenwaveguide display assembly 210 and eyeball 220.

In some examples, waveguide display assembly 210 includes a stack of oneor more waveguide displays including, but not restricted to, a stackedwaveguide display, a varifocal waveguide display, etc. The stackedwaveguide display is a polychromatic display (e.g., a RGB display)created by stacking waveguide displays whose respective monochromaticsources are of different colors. The stacked waveguide display is also apolychromatic display that can be projected on multiple planes (e.g.,multi-planar colored display). In some configurations, the stackedwaveguide display is a monochromatic display that can be projected onmultiple planes (e.g., multi-planar monochromatic display). Thevarifocal waveguide display is a display that can adjust a focalposition of image light emitted from the waveguide display. In alternateexamples, waveguide display assembly 210 may include the stackedwaveguide display and the varifocal waveguide display.

FIG. 3 illustrates an isometric view of an example of a waveguidedisplay 300. In some examples, waveguide display 300 is a component(e.g., waveguide display assembly 210) of near-eye display 100. In someexamples, waveguide display 300 is part of some other near-eye displayor other system that directs image light to a particular location.

Waveguide display 300 includes a source assembly 310, an outputwaveguide 320, and a controller 330. For purposes of illustration, FIG.3 shows the waveguide display 300 associated with a single eyeball 220,but in some examples, another waveguide display separate, or partiallyseparate, from the waveguide display 300 provides image light to anothereye of the user.

Source assembly 310 generates image light 355. Source assembly 310generates and outputs image light 355 to a coupling element 350 locatedon a first side 370-1 of output waveguide 320. Output waveguide 320 isan optical waveguide that outputs expanded image light 340 to an eyeball220 of a user. Output waveguide 320 receives image light 355 at one ormore coupling elements 350 located on the first side 370-1 and guidesreceived input image light 355 to a directing element 360. In someexamples, coupling element 350 couples the image light 355 from sourceassembly 310 into output waveguide 320. Coupling element 350 may be, forexample, a diffraction grating, a holographic grating, one or morecascaded reflectors, one or more prismatic surface elements, and/or anarray of holographic reflectors.

Directing element 360 redirects the received input image light 355 todecoupling element 365 such that the received input image light 355 isdecoupled out of output waveguide 320 via decoupling element 365.Directing element 360 is part of, or affixed to, first side 370-1 ofoutput waveguide 320. Decoupling element 365 is part of, or affixed to,second side 370-2 of output waveguide 320, such that directing element360 is opposed to the decoupling element 365. Directing element 360and/or decoupling element 365 may be, for example, a diffractiongrating, a holographic grating, one or more cascaded reflectors, one ormore prismatic surface elements, and/or an array of holographicreflectors.

Second side 370-2 represents a plane along an x-dimension and ay-dimension. Output waveguide 320 may be composed of one or morematerials that facilitate total internal reflection of image light 355.Output waveguide 320 may be composed of for example, silicon, plastic,glass, and/or polymers. Output waveguide 320 has a relatively small formfactor. For example, output waveguide 320 may be approximately 50 mmwide along x-dimension, 30 mm long along y-dimension and 0.5-1 mm thickalong a z-dimension.

Controller 330 controls scanning operations of source assembly 310. Thecontroller 330 determines scanning instructions for the source assembly310. In some examples, the output waveguide 320 outputs expanded imagelight 340 to the user's eyeball 220 with a large field of view (FOV).For example, the expanded image light 340 is provided to the user'seyeball 220 with a diagonal FOV (in x and y) of 60 degrees and/orgreater and/or 150 degrees and/or less. The output waveguide 320 isconfigured to provide an eyebox with a length of 20 mm or greater and/orequal to or less than 50 mm; and/or a width of 10 mm or greater and/orequal to or less than 50 mm.

Moreover, controller 330 also controls image light 355 generated bysource assembly 310, based on image data provided by image sensor module370. Image sensor module 370 may be located on first side 370-1 and mayinclude, for example, image sensor modules 120 a-120 d of FIG. 1A togenerate image data of a physical environment in front of the user(e.g., for location determination). Image sensor module 370 may also belocated on second side 370-2 and may include image sensor modules 150 aand 150 b of FIG. 1B to generate image data of eyeball 220 (e.g., forgaze point determination) of the user. Image sensor module 370 mayinterface with a remote console that is not located within waveguidedisplay 300. Image sensor module 370 may provide image data to theremote console, which may determine, for example, a location of theuser, a gaze point of the user, etc., and determine the content of theimages to be displayed to the user. The remote console can transmitinstructions to controller 330 related to the determined content. Basedon the instructions, controller 330 can control the generation andoutputting of image light 355 by source assembly 310.

FIG. 4 illustrates an example of a cross section 400 of the waveguidedisplay 300. The cross section 400 includes source assembly 310, outputwaveguide 320, and image sensor module 370. In the example of FIG. 4,image sensor module 370 may include a set of pixel cells 402 located onfirst side 370-1 to generate an image of the physical environment infront of the user. In some examples, there can be a mechanical shutter404 interposed between the set of pixel cells 402 and the physicalenvironment to control the exposure of the set of pixel cells 402. Insome examples, the mechanical shutter 404 can be replaced by anelectronic shutter gate, as to be discussed below. Each of pixel cells402 may correspond to one pixel of the image. Although not shown in FIG.4, it is understood that each of pixel cells 402 may also be overlaidwith a filter to control the frequency range of the light to be sensedby the pixel cells.

After receiving instructions from the remote console, mechanical shutter404 can open and expose the set of pixel cells 402 in an exposureperiod. During the exposure period, image sensor module 370 can obtainsamples of lights incident on the set of pixel cells 402, and generateimage data based on an intensity distribution of the incident lightsamples detected by the set of pixel cells 402. Image sensor module 370can then provide the image data to the remote console, which determinesthe display content, and provide the display content information tocontroller 330. Controller 330 can then determine image light 355 basedon the display content information.

Source assembly 310 generates image light 355 in accordance withinstructions from the controller 330. Source assembly 310 includes asource 410 and an optics system 415. Source 410 is a light source thatgenerates coherent or partially coherent light. Source 410 may be, forexample, a laser diode, a vertical cavity surface emitting laser, and/ora light emitting diode.

Optics system 415 includes one or more optical components that conditionthe light from source 410. Conditioning light from source 410 mayinclude, for example, expanding, collimating, and/or adjustingorientation in accordance with instructions from controller 330. The oneor more optical components may include one or more lenses, liquidlenses, mirrors, apertures, and/or gratings. In some examples, opticssystem 415 includes a liquid lens with a plurality of electrodes thatallows scanning of a beam of light with a threshold value of scanningangle to shift the beam of light to a region outside the liquid lens.Light emitted from the optics system 415 (and also source assembly 310)is referred to as image light 355.

Output waveguide 320 receives image light 355. Coupling element 350couples image light 355 from source assembly 310 into output waveguide320. In examples where coupling element 350 is diffraction grating, apitch of the diffraction grating is chosen such that total internalreflection occurs in output waveguide 320, and image light 355propagates internally in output waveguide 320 (e.g., by total internalreflection), toward decoupling element 365.

Directing element 360 redirects image light 355 toward decouplingelement 365 for decoupling from output waveguide 320. In examples wheredirecting element 360 is a diffraction grating, the pitch of thediffraction grating is chosen to cause incident image light 355 to exitoutput waveguide 320 at angle(s) of inclination relative to a surface ofdecoupling element 365.

In some examples, directing element 360 and/or decoupling element 365are structurally similar. Expanded image light 340 exiting outputwaveguide 320 is expanded along one or more dimensions (e.g., may beelongated along x-dimension). In some examples, waveguide display 300includes a plurality of source assemblies 310 and a plurality of outputwaveguides 320. Each of source assemblies 310 emits a monochromaticimage light of a specific band of wavelength corresponding to a primarycolor (e.g., red, green, or blue). Each of output waveguides 320 may bestacked together with a distance of separation to output an expandedimage light 340 that is multi-colored.

FIG. 5 is a block diagram of an example of a system 500 including thenear-eye display 100. The system 500 comprises near-eye display 100, animaging device 535, an input/output interface 540, and image sensormodules 120 a-120 d and 150 a-150 b that are each coupled to controlcircuitries 510. System 500 can be configured as a head-mounted device,a wearable device, etc.

Near-eye display 100 is a display that presents media to a user.Examples of media presented by the near-eye display 100 include one ormore images, video, and/or audio. In some examples, audio is presentedvia an external device (e.g., speakers and/or headphones) that receivesaudio information from near-eye display 100 and/or control circuitries510 and presents audio data based on the audio information to a user. Insome examples, near-eye display 100 may also act as an AR eyewear glass.In some examples, near-eye display 100 augments views of a physical,real-world environment, with computer-generated elements (e.g., images,video, sound, etc.).

Near-eye display 100 includes waveguide display assembly 210, one ormore position sensor modules 525, and/or an inertial measurement unit(IMU) 530. Waveguide display assembly 210 includes source assembly 310,output waveguide 320, and controller 330.

IMU 530 is an electronic device that generates fast calibration dataindicating an estimated position of near-eye display 100 relative to aninitial position of near-eye display 100 based on measurement signalsreceived from one or more of position sensor modules 525.

Imaging device 535 may generate image data for various applications. Forexample, imaging device 535 may generate image data to provide slowcalibration data in accordance with calibration parameters received fromcontrol circuitries 510. Imaging device 535 may include, for example,image sensor modules 120 a-120 d of FIG. 1A for generating image data ofa physical environment in which the user is located, for performinglocation tracking of the user. Imaging device 535 may further include,for example, image sensor modules 150 a-150 b of FIG. 1B for generatingimage data for determining a gaze point of the user, to identify anobject of interest of the user.

The input/output interface 540 is a device that allows a user to sendaction requests to the control circuitries 510. An action request is arequest to perform a particular action. For example, an action requestmay be to start or end an application or to perform a particular actionwithin the application.

Control circuitries 510 provide media to near-eye display 100 forpresentation to the user in accordance with information received fromone or more of: imaging device 535, near-eye display 100, andinput/output interface 540. In some examples, control circuitries 510can be housed within system 500 configured as a head-mounted device. Insome examples, control circuitries 510 can be a standalone consoledevice communicatively coupled with other components of system 500. Inthe example shown in FIG. 5, control circuitries 510 include anapplication store 545, a tracking module 550, and an engine 555.

The application store 545 stores one or more applications for executionby the control circuitries 510. An application is a group ofinstructions, that, when executed by a processor, generates content forpresentation to the user. Examples of applications include: gamingapplications, conferencing applications, video playback applications, orother suitable applications.

Tracking module 550 calibrates system 500 using one or more calibrationparameters and may adjust one or more calibration parameters to reduceerror in determination of the position of the near-eye display 100.

Tracking module 550 tracks movements of near-eye display 100 using slowcalibration information from the imaging device 535. Tracking module 550also determines positions of a reference point of near-eye display 100using position information from the fast calibration information.

Engine 555 executes applications within system 500 and receives positioninformation, acceleration information, velocity information, and/orpredicted future positions of near-eye display 100 from tracking module550. In some examples, information received by engine 555 may be usedfor producing a signal (e.g., display instructions) to waveguide displayassembly 210 that determines a type of content presented to the user.For example, to provide an interactive experience, engine 555 maydetermine the content to be presented to the user based on a location ofthe user (e.g., provided by tracking module 550), or a gaze point of theuser (e.g., based on image data provided by imaging device 535), adistance between an object and user (e.g., based on image data providedby imaging device 535).

FIG. 6A and FIG. 6B illustrate examples of an image sensor module 600and its operations. Image sensor module 600 can be part of image sensormodules 120 a-120 d and 150 a-150 b of FIG. 1A and FIG. 1B, and part ofimage sensor module 370 of FIG. 3. As shown in FIG. 6A, image sensormodule 600 includes one or more lenses 602 and an image sensor 604,which can include one or more image sensor dies/chips. One or morelenses 602 can include a single lens 602 (e.g., as shown in FIG. 6A andFIG. 6B) or multiple lens aligned in a stack along a propagationdirection of light (e.g., along the z-axis). One or more lenses 602 cangather light 606 and light 608 and focus light 606 and light 608 towardsimage sensor 604. Image sensor 604 includes a light receiving surface610 to receive the focused light 606. Light receiving surface 610 can beseparated from lens 602 by a distance f. The distance fin FIG. 6A cancorrespond to a distance between lens 602 and image sensor 604 forcapturing an image of an object at an infinite distance away from lens602. Distance f can be adjusted based on, for example, the distancebetween the object and lens 602. Provided that light receiving surface610 is at distance f from lens 602, that light receiving surface 610 isperpendicular to the optical axis 612 of lens 602, and that center oflight receiving surface 610 aligns with optical axis 612, lightreceiving surface 610 can receive focused light with a field of view 620defined based on the length f of lens 602. Image sensor 604 furtherincludes an array of pixel cells 605 below the light receiving surface610 to convert the focused light 606 to electrical signals. Differentpixel cells may receive different intensities of light via lens 602 togenerate the electrical signals, and an image of field of view 620 canbe constructed based on the electrical signals from the pixel cells.

The optical properties of Image sensor module 600, such as field of view620, can be determined by the physical properties of lens 602.Specifically, the curvature and refractive index of lens 602 candetermine the focal length f. Moreover, the Abbe number of lens 602 candetermine the variation of refractive index versus wavelength. Further,the birefringence of lens 602 can determine the variation of therefractive index of the lens with respect to the polarization andpropagation direction of the incident light. Both Abbe number andbirefringence can control the dispersion of light 606 by lens 602 andcan be determined by the material of lens 602. All these opticalproperties can affect the quality of an image (e.g., amount ofinformation captured in the field of view, blurriness and distortioncaused by the dispersion of light) captured by the image sensor module600.

The assembly of one or more lenses 602 and image sensor 604 in imagesensor module 600 can also affect the optical properties as well as theperformance of image sensor module 600. Specifically, the alignment ofthe image sensor with respect to the lens (e.g., relative orientations,positions) can also affect the reception of the light by image sensor604. As described above, for proper alignment, light receiving surface610 should be separated from lens 602 by the distance f. Moreover, lightreceiving surface 610 should be perpendicular to the optical axis 612 oflens 602, whereas the center of light receiving surface 610 should alignwith optical axis 612. FIG. 6B illustrates examples of misalignmentbetween lens 602 and image sensor 604 and their effects. As shown inFIG. 6B, image sensor 604 (and light receiving surface 610) can becometilted with respect to optical axis 612 and lens 602. As a result,various locations of light receiving surface 610 (e.g., locationslabelled “P” and “Q”) may be separated from lens 602 by a distance thatis either shorter than or longer than distance f. As a result, lightreceiving surface 610 may receive dispersed light 606 at locations P andQ, and the resulting image may appear to be out-of-focus at thoselocations and become distorted. In addition, the center of lightreceiving surface 610 does not align with optical axis 612, which canreduce the field of view captured by light receiving surface 610.

FIG. 7 illustrates an example of an image sensor module 700 that canprovide improved alignment between lens 602 and image sensor 604. Asshown in FIG. 7, image sensor module 700 includes a housing 701 thathouses one or more lenses 602, a substrate 703 (e.g., a glasssubstrate), and image sensor 604. One or more lenses 602 can includemultiple lenses forming a lens stack and mounted on the internal wall ofhousing 701. Housing 701 further includes a shoulder structure 706 thatare on the vertical sides of image sensor 604 (e.g., sides that areperpendicular to light receiving surface 610). There can be an air gap716 between the vertical sides of image sensor 604 and shoulderstructure 706, and an air gap 718 between one or more lenses 602 andlight receiving surface 610 of image sensor 604. Both air gaps 716 and718 can provide space for aligning one or more lenses 602 with respectto image sensor 604.

Both housing 701 and image sensor 604 are bonded onto a PCB 720. Forexample, shoulder structure 706 can be bonded to PCB 720 via an adhesivebondline 722, whereas image sensor 604 can be soldered onto PCB 720 viasolder balls 724 to form conductive bonds. Bondline 722 can be used toalign one or more lenses 602 with respect to image sensor 604.Specifically, bondline 722 can include adhesives that are flexible whenin a liquid state but can become hardened when cured. When bondline 722is in a liquid state, housing 701 (with one or more lenses 602 mountedwithin) can be moved in the x, y, and z directions and/or rotated aroundthe x, y, and z axes to align with image sensor 604. The targetalignment can be such that, for example, optical axis 612 of one or morelenses 602 aligns with the center of the image sensor 604, lightreceiving surface 610 is perpendicular to the optical axis 612 and isseparated from one or more lenses 602 by a pre-determined distance d,etc. Once the target alignment is achieved, the adhesives can be curedto form bondline 722 to fix the location and orientation of the one ormore lenses 602 with respect to image sensor 604.

Although housing 701 of FIG. 7 can provide improved alignment betweenone or more lenses 602 and image sensor 604, the shoulder structure 706of housing 701 increases the footprint of image sensor module 700, whichis undesirable for a wearable device such as near-eye display 100. Asexplained above, the increased footprint of image sensor module 700 canlead to increase in the thickness of frame 105, which can increase theweight of frame 105, reduce the area of display 110, and affectaesthetics, all of which can degrade the user experience. Meanwhile, inorder to shrink the footprint of image sensor module 700, the footprintof image sensor 604 may need to shrink, which can reduce the number ofpixel cells included in image sensor 604 and reduce the resolution ofimage capture. The performance of image sensor module 700 may bedegraded as a result.

FIG. 8A illustrates another example of an image sensor module 800 withreduced footprint, whereas FIG. 8B and FIG. 8C illustrate an examplefabrication method of image sensor module 800. As shown in FIG. 8B,image sensor module 800 may include lens 602 a (of one or more lenses602) formed on a glass substrate 802. Glass substrate 802 can be bondedto image sensor 604 via, for example, an bonding layer 804. Additionalglass substrates can be stacked on top of glass substrate 802 to includeadditional lens. For example, a glass substrate 806 having a cavity 808can be stacked on top of glass substrate 802 with cavity 808accommodating lens 602 a, and another glass substrate 810 including lens602 b can be stacked on top of glass substrates 806 and 802, with lenses602 a and 602 b aligned along the same optical axis 612. Image sensor604 can be soldered onto PCB 720 via solder balls 724 to form conductivebonds.

Compared with image sensor module 700 of FIG. 7, image sensor module 800can provide a reduced footprint. Specifically, as shown in FIG. 8A, thefootprint of glass substrates 802, 806, and 810 can be substantially thesame or smaller than image sensor 604, unlike image sensor module 700where shoulder structure 706 extends outwards from image sensor 604. Asa result, the footprint of image sensor module 800 (represented by L₈₀₀)can be substantially the same as the footprint of image sensor 604(represented by L₆₀₄).

The glass substrates in image sensor module 700 can also provide acertain degree of alignment between lens 602 and image sensor 604, suchas defining the vertical distance (labelled “d” in FIG. 8A) between thelens and the image sensor die. However, the degree of alignment can belimited by the fabrication of image sensor module 700 which is typicallybased on a wafer-level optics process.

FIG. 8B illustrates an example of a wafer-level optics process. As shownin FIG. 8B, multiple lenses 602 a can be formed on a glass wafer 822.Moreover, multiple cavities 808 can be formed on a glass wafer 824,whereas multiple lenses 602 b can be formed on a glass wafer 826. Glasswafers 822, 824, and 826 can be stacked, and each glass wafer can bemoved along the x and y axes to align each lens 602 a, cavity 808, andlens 602 b along the same optical axis 612 as shown in FIG. 8A. Analignment process can be performed to align glass wafers 822, 824, and826. Specifically, images of alignment marks 832, 834, and 836 on,respectively, glass wafers 822, 824, and 826 can be captured by cameras840 and 842, and a degree of alignment among the wafers can bedetermined based on the images. Each wafer can be moved against eachother until the images of alignment marks 832, 834, and 836 indicatethat a target degree of alignment is reached. After the glass wafers arestacked and aligned, the glass wafer stack can then be stacked on asemiconductor wafer 850 including multiple image sensor dies 852, witheach die corresponding to image sensor 604. The glass wafer stack canalso be moved along the x and y axes to align the lens with the imagesensor dies 604. The alignment of the glass wafer stack with respect tosemiconductor wafer 850 can also be based on images of alignment marks832/834/836 of the glass wafer stack and alignment mark 854 onsemiconductor wafer 850 captured by cameras 840 and 842. After thealignment process completes, the glass wafer stack and the image sensordies can be diced to form individual image sensor module 800.

The alignment process in FIG. 8B can only provide a limited degree ofalignment between lens 602 and image sensor 604. This is because thealignment is on a wafer-level and cannot completely eliminate thelocation/orientation differences of lens 602 between different imagesensor modules. FIG. 8C illustrates an example of the limited alignment.As shown in FIG. 8C, two lens 602 a 1 and 602 a 2 are separated by ahorizontal distance d1 and a vertical distance Δz on glass wafer 822,whereas two image sensor dies 852 a and 852 b are separated by ahorizontal distance d2 on semiconductor wafer 850. Based on alignmentbetween glass wafer 822 and semiconductor wafer 850, each of lenses 602a 1 and 602 a 2 may misalign with, respectively, image sensor dies 852 aand 852 b by half of the difference between d1 and d2. Moreover, aswafer 826 is only moved along the x/y axes to align with semiconductorwafer 850, the misalignment along the vertical axis, caused by Δz, mayremain for image sensor die 852 b. Moreover, there is also no rotationof wafer 626 (or image sensor 604) around the x, y, and z axes tocorrect the alignment.

In some examples, the alignment between the stack of glass substrates802, 806, and 810 and image sensor 604 in the wafer-level optics processcan be performed after the glass substrates stack are diced to form alens stack (including diced glass substrates 802, 806, and 810 as wellas lenses 602 a and 602 b) for each image sensor 604. The lens stack canbe moved with respect to an image sensor 604 and along the x/y axesbased on, for example, alignment between edges of the lens stack andfeatures of image sensor 604. However, there is also no rotation ofwafer 626 (or image sensor 604) around the x, y, and z axes to correctthe alignment. Therefore, only a limited degree of alignment betweenlens 602 and image sensor 604 can be achieved.

FIG. 9A-FIG. 9C illustrate examples of an image sensor module that canprovide both reduced footprint and improved optical properties. As shownin FIG. 9A, an image sensor module 900 can include a lens assembly 902and image sensor 604 of FIG. 7. Image sensor 604 can be positioned belowlens assembly 902 and can be bonded to lens assembly 902 via a bondinglayer 904. As lens assembly 902 does not include any shoulder structuresthat are adjacent to the sides of image sensor 604, lens assembly 902does not add to the footprint of image sensor module 900. The footprintof image sensor module 900 is mostly contributed by image sensor 604.

Lens assembly 902 can include one or more layers 908 and one or morespacers 910, with each layer having a lens portion formed as lens 602and an extension portion 911. The lens portion is configured to gatherand direct light towards image sensor 604, whereas extension portion 911can provide mechanical support for the lens portion. For example,extension portion 911 can rest on or be supported by spacer 910, whichincludes an opening to fit the lens portion of layer 908. Each layer canbe made of, for example, a polymer material such as a cyclic olefincopolymer (COC) material which can provide a lower Abbe number andreduced birefringence, both of which can reduce light dispersion by lens602. Other polymer materials that can be used to fabricate layers 908may include, for example, APEL5014CL, OKP1, OKP4, EP8000. APEL5014CL canbe a COC. OKP1 and OKP4 can be a polyester, whereas EP8000 can be apolycarbonate. Each layer can also be made of other materials such as,for example, glass. Spacers 910 can also be made of an opaque materialsuch as, for example, an opaque polymer, metal, etc.

In a case where lens assembly 902 includes multiple lenses 602 (e.g.,three lenses 602 a, 602 b, and 602 c as shown in FIG. 9A), each layer908 (e.g., layers 908 a, 908 b, and 908 c) can stack on top of eachother and bonded to a spacer 910, which can provide mechanical supportand define the location and orientation of lens 602 within lens assembly902. For example, extension portion 911 a of layer 908 a can be bondedto spacer 910 a, which includes an opening 920 for outputting light toimage sensor 604. In some examples, opening 920 can be filled with partof lens 602 a to form a light outputting surface. Moreover, spacer 910 bcan be inserted between layers 908 b and 908 a with extension portion911 b of layer 908 b bonded to spacer 910 b, whereas spacer 910 c can beinserted between layers 908 c and 908 b with extension portion 911 c oflayer 908 c bonded to spacer 910 c. Lens assembly 902 further includes atop cover 914 which includes an aperture 916 for receiving incidentlight.

In some examples, an opaque/dark coating layer 930 (shown in FIG. 9B)can be applied on the external vertical surfaces of lens assembly 902 toprevent light from entering through the side of lens assembly 902 toensure that light only enters through aperture 916. In some examples, asshown in FIG. 11B,

In some examples, some of the spacers 910 between layers 908 can beomitted in lens assembly 902. The extension portion 911 and/or lens 602of two layers 908 can be bonded to form a stack. For example, extension911 c of layer 908 c and extension 911 b of layer 908 b can be bondedtogether, whereas extension 911 b of layer 908 b and extension 911 a oflayer 908 a can also be bonded together, to form lens assembly 902. Asanother example, lenses 602 c and 602 b can be bonded together, whereas602 b and 602 c can also be bonded together, to form lens assembly 902.

Layers 908 a, 908 b, and 908 c can be fabricated by high precisionprocesses, such as injection molding, to provide improved control overthe physical dimensions (e.g., curvatures) of lenses 602 a, 602 b, and602 c and the resulting optical properties of lens assembly 902.Moreover, spacers 910 a, 910 b, and 910 c, as well as top cover 914, canalso be fabricated by injection molding to provide tighter fit betweenthe layers, the spacers, and the covers, which can improve the rigidityof lens assembly 902. In some examples, spacers 910 a, 910 b, and 910 c,as well as top cover 914 can be made of stamped or machined metal.

Image sensor 604, which can include glass substrate 703 (shown as aseparate component in the figures), can be bonded to lens assembly 902via a bonding layer 904. Bonding layer 904 can be formed by applying alayer of adhesive material onto image sensor 604 after image sensor 604is soldered onto PCB 720 via solder balls 724 in a reflow process. Imagesensor 604 (soldered onto PCB 720) and lens assembly 902 can then bebrought together so that spacer 910 a comes into contact with theadhesive material. The adhesive material can then be hardened in acuring process to form bonding layer 904, which can provide permanentbonding between image sensor 604 and lens assembly 902.

Bonding layer 904 can be used to maintain the alignment between imagesensor 604 with lens 602 of lens assembly 902 obtained from an alignmentprocess prior to the curing process, when the adhesive material remainsin a liquid state. FIG. 9B illustrates an example of the alignmentprocess, in which the position and orientation of image sensor 604 withrespect to lens assembly 902 can be adjusted based on sensor datagenerated by image sensor 604 which reflects a degree of alignment.Referring to FIG. 9B, image sensor 604 can be enabled (powered on) tosense light that passes through lens assembly 902 during the alignmentprocess. In one example, lens assembly 902 can be held at a fixedlocation and a fixed orientation, whereas image sensor 604 (and PCB 720)can be supported on a platform (not shown in FIG. 9B) that can supportsix degrees of movements including linear movements along each of the x,y, and z axes, as well as rotations about each of the x, y, and z axes.In another example, image sensor 604 (and PCB 720) can be held at afixed location and a fixed orientation, whereas lens assembly 902 can bemoved/rotated. A light projector 940 can project a light pattern 950(e.g., a two-dimensional light pattern of an image) to lens assembly902, which can direct light pattern 950 towards image sensor 604, whichcan generate sensor data 960 of the image based on the sensing of lightpattern 950. As described above, a degree of alignment between imagesensor 604 and lens 602 (e.g., how far image sensor 604 is from thefocal point of lens 602, or the orientation and position of image sensor604 with respect to optical axis 612 of lens 602) can determine aquality of image generated by image sensor 604 from the sensing of lightpattern 950. A controller 970 can analyze sensor data 960 to determine,for example, a degree of blurriness, a degree of distortion, etc., ofthe image represented by sensor data 960, from which controller 970 candetermine a degree of alignment between image sensor 604 and lens 602.Based on the degree of alignment, controller 970 can control a movementof lens assembly 902 and/or image sensor 604 (e.g., based on linearmovements along each of the x, y, and z axes, rotations about each ofthe x, y, and z axes, etc.) to align image sensor 604 with respect tolens assembly 902 when the adhesive between image sensor 604 and lensassembly 902 remains in the liquid state. The adhesive can be squeezedor stretched to allow the movement.

Controller 970 can continue moving at least one of image sensor 604 orlens assembly 902 to adjust the alignment until a target degree ofalignment is reached. For example, a target degree of alignment isreached when optical axis 612 (not shown in FIG. 9A) of one or morelenses 602 aligns with the center of the image sensor 604, lightreceiving surface 610 is perpendicular to the optical axis 612 and isseparated from one or more lenses 602 by a pre-determined distance, etc.When the target degree of alignment is reached, the adhesive can behardened in a curing process. The curing process can be based on, forexample, ultraviolet light, a thermal process at a temperature lowerthan the melting point of the polymer lens (to avoid deforming thelens), or both. When the adhesive is hardened, bonding layer 904 can beformed to bond image sensor 604 with lens assembly 902 while maintainingimage sensor 604 at the aligned position and orientation with respect tolens assembly 902. As image sensor 604 can be moved with respect to lensassembly 902 based on linear movements along each of the x, y, and zaxes, rotations about each of the x, y, and z axes, and based on sensordata generated by image sensor 604 which can provide an accurate accountof the instantaneous degree of alignment, the achievable degree ofachievable alignment between lens 602 and image sensor 604 can besubstantially increased.

There are various ways of distributing the adhesive to form bondinglayer 904. In one example, as shown in the left diagram of FIG. 9C,bonding layer 904 can be formed around a perimeter of image sensor 604surrounding a region 932. Region 932 can be over light receiving surface610 of image sensor 604 and faces opening 920 of spacer 910 a of lensassembly 902. With such arrangements, adhesives that become opaque orotherwise have a low light transmittance upon becoming hardened can beused to form bonding layer 904 without blocking the light from reachingimage sensor 604, but the application of the adhesive is restricted suchthat the adhesives do not spill into region 932 when squeezed during thealignment process. In another example, as shown in the right diagram ofFIG. 9C, bonding layer 904 can be formed over region 932 to bond with,for example, the part of lens 602 a that fills opening 920. With sucharrangements, there can be fewer restrictions on the application of theadhesive on image sensor 604, but the adhesive needs to be transparentor at least have a high light transmittance upon becoming hardened bythe curing process. In some examples, the adhesive can also be formed onlens assembly 902 (e.g., on a surface of spacer 910 a facing imagesensor 604) to bond with image sensor 604.

FIG. 10 illustrates another example of an image sensor module that canprovide both reduced footprint and improved optical properties. As shownin FIG. 10, an image sensor module 1000 can include a lens assembly 1002and image sensor 604 of FIG. 7. Lens assembly 1002 can include anopaque/dark lens housing 1004, which can be in the form of a barrel,that holds one or more lenses 602. Housing 1004 can be made of, forexample, a polymer material, a metal, etc. Image sensor 604 can bepositioned below housing 1004 and can be bonded to lens assembly 1002via bonding layer 904. As lens assembly 1002 does not include anyshoulder structure that are adjacent to the sides of image sensor 604,lens assembly 1002 does not add to the footprint of image sensor module1000. The footprint of image sensor module 1000 is mostly contributed byimage sensor 604.

In some examples, as shown in FIG. 10, each of one or more lenses 602can be part of a layer 1006 including an extension portion 1008. Lensassembly 1002 may also include one or more spacers 1010. The lensportion of layer 1006 is configured to gather and direct light towardsimage sensor 604, whereas the extension portion 1008 can providemechanical support to the lens portion. For example, extension portion1008 can rest on or be supported by spacer 1010, which includes anopening to fit the lens portion of layer 1006. Each layer 1006 andspacer 1010 are mechanically coupled (e.g., via adhesive) to the innerwall of housing 1004. Each layer 1006 can be made of the same materialas layer 908 including, for example, a polymer material (e.g., COC,polycarbonate), a glass material, etc. Spacers 1010 can also be made ofan opaque material such as polymer and metal. In a case where lensassembly 902 includes multiple lenses 602 (e.g., three lenses 602 a, 602b, and 602 c as shown in FIG. 10), each layer 1006 (e.g., layers 1006 a,1006 b, and 1006 c) can stack on top of each other and separated by aspacer 1010, which can provide mechanical support and define thelocation and orientation of lens 602 within lens assembly 1002. Forexample, extension portion 1008 a of layer 1006 a and extension portion1008 b of layer 1006 b can be separated by spacer 1010 a, whereasextension portion 1008 b of layer 1006 b and extension portion 1008 c oflayer 1006 c can be separated by spacer 1010 b. Housing 1004 furtherincludes an aperture 1016 for receiving incident light.

Similar to image sensor module 900, each layer 1006 can be fabricated byhigh precision processes, such as injection molding, to provide improvedcontrol over the physical dimensions (e.g., curvatures) of lenses 602 a,602 b, and 602 c and the resulting optical properties of lens assembly1002. Moreover, spacers 1010 can also be fabricated by injectionmolding, machined/stamped metals, etc., to provide tighter fit betweenthe layers and the spacers to improve the rigidity of lens assembly1002. Moreover, bonding layer 904 can be used to maintain the alignmentbetween image sensor 604 (of image sensor 604) with lens 602 of lensassembly 1002 obtained from an alignment process as described in FIG.9B.

In some examples, the optical elements of an image sensor module, suchas image sensor modules 700, 800, 900, and 1000 of FIG. 7-FIG. 10, mayinclude a filter. The filter can include a filter array to selectdifferent frequency components of the light to be detected by differentpixel cells the image sensor, or a single frequency component of thelight to be detected by all pixel cells. The image sensor includes lightsensing elements (e.g., photodiodes) that can receive the differentfrequency components of the light selected by the filter array via thelight receiving surface and convert the frequency components toelectrical signals. The electrical signals can represent, for example,intensities of the different frequency components of light from a scene.

FIG. 11A, FIG. 11B, and FIG. 11C illustrate examples of an image sensormodule 1100 including a filter. Image sensor module 1100 can be part ofimage sensor modules 120 a-120 d and 150 a-150 b of FIG. 1A, FIG. 1B,and FIG. 1C, and part of image sensor module 370 of FIG. 3. Image sensormodule 1100 may include components of image sensor modules 700, 800,900, and 1000 of FIG. 7-FIG. 10, such as one or more lenses 602 andimage sensor 604. As shown on the left of FIG. 11A, which represents aninternal side view of image sensor module 1100, image sensor module 1100includes one or more lenses 602, a filter 1103, and image sensor 604including an array of pixel cells 605 as shown in FIG. 6A. One or morelenses 602 (shown as an unified body in FIG. 11A for simplicity) caninclude a single lens or multiple lens separated by spacers and alignedin a stack along a propagation direction of light (e.g., along thez-axis) to pass the light, as shown in FIG. 7-FIG. 10. In some examples,the light can be focused and can converge at a focal point. The lightcan be filtered by filter 1103, which can select one or more frequencycomponents of the light to be detected by image sensor 604. In someexamples, filter 1103 can select a single frequency range (e.g., avisible frequency range, an infrared frequency range, etc.) of light tobe detected by image sensor 604. In some examples, filter 1103 caninclude a filter array to select different frequency ranges (e.g., a redfrequency range, a blue frequency range, a green frequency range, aninfrared frequency range) of light to be detected by image sensor 604.

Array of pixel cells 605 below light receiving surface 610 of imagesensor 604 can convert different frequency components of the light toelectrical signals. The electrical signals can represent, for example,intensities of the different frequency components of light from a scene.Based on the electrical signals, an image processor can generate animage of the scene. The image sensor module can be soldered onto aprinted circuit board (PCB) 720 which also includes an image processor(not shown in the figures). PCB 720, as described in FIG. 7, includeselectrical traces to transmit the electrical signals from the imagesensor module to the image processor, which can generate an image of thescene based on the electrical signals.

Image sensor module 1100 includes a holder structure 1120 to hold andphysically support one or more lenses 602 and filter 1103. Specifically,as shown in FIG. 11A, holder structure 1120 may include a housing 1122,which can be include housing 1004 of FIG. 10, and a retainer 1124. Bothhousing 1122 and retainer 1124 can be made of, for example, apolycarbonate (PC) material, and/or a polymer material (e.g., liquidcrystal polymer, LCP) using injection molding. Housing 1122, which canbe in the form of a barrel, includes a top opening 1132 to receive lightand a bottom opening 1134 to output light to image sensor 1104.Referring to FIG. 11B, one or more lenses 602 can be loaded into housing1122 through bottom opening 1134 towards top opening 1132 (indicated bydirection labelled “A”). One or more lenses 602 can be mounted atpre-determined positions within housing 1122 between top opening 1132and bottom opening 1134 to form a lenses stack, where housing 1122 canprovide physical support to the lenses stack. In addition, housing 1122is stacked on image sensor 604 along the z-axis.

Referring back to FIG. 11A, bottom surface 1136 of housing 1122, whichsurrounds bottom opening 1134, can be bonded to light receiving surface1110 of image sensor 604 via, for example, an adhesive 1138 followed byUV curing to harden the adhesive, similar to the formation of bondinglayer 804/904 in FIG. 8A-FIG. 10. Based on the bonding with image sensor604, housing 1122 can set the orientation and position of one or morelenses 602 with respect to image sensor 604. In some examples, bottomsurface 1136 is bonded to the image sensor die of image sensor 1104. Insome examples, bottom surface 1136 is bonded to other components ofimage sensor 604, such as glass substrate 703 (not shown in FIG. 11A), apackage of image sensor 604, etc.

In addition, retainer 1124 can be mounted within housing 1122 betweenthe lenses stack and bottom opening 1134. Referring to FIG. 11C,retainer 1124 can include an upper surface 1139 (highlighted with adotted line) to support one or more lenses 602 to prevent the lensesfrom falling out of bottom opening 1134, and a middle surface 1140(highlighted with a dotted line) to mount filter 1103 (e.g., via a layerof adhesive not shown in the figures). Retainer 1124 is positioned awayfrom bottom opening 1134 and further includes a recessed bottom surface1141 to prevent retainer 1124 from protruding out of housing, whenaccounting for tolerance in the placement of retainer 1124 withinhousing 1122. Such arrangements can ensure that bottom surface 1136 ofhousing 1122 is in contact with image sensor 604 when holder structure1120 is placed on image sensor 604, while no part of retainer 1124 is incontact with image sensor 604. To maintain the position of retainer 624within housing 1122, an adhesive 1142 can be applied on recessed bottomsurface 641 of retainer 1124 and inner wall of housing 1122, followed byUV curing, to bond housing 1122 with retainer 1124.

Although FIG. 11A illustrates that housing 1122 includes a cylindricalportion and a rectangular/square portion, and that bottom opening 1134has a circular shape, it is understood that housing 1122 and bottomopening 1134 can have other geometric shapes. For example, housing 1122can include only a cylindrical barrel, a rectangular/square barrel,etc., whereas the bottom opening can have a rectangular/square shape.

The arrangements of FIG. 11A-FIG. 11C, in which housing 1122 is attachedon image sensor 604 to form a stack, can reduce the footprint of theimage sensor module 1100 on PCB 720. The reduced footprint can bedesirable especially for integrating image sensor module 600 in a mobiledevice, such as near-eye display 100, where space is very limited. Forexample, referring back to FIG. 1C, in order to fit image sensor module1100 into frame 105, a width of image sensor module 1100 needs to bemade shorter than the thickness (t) of frame 105. Moreover, a length ofimage sensor 600 (e.g., of sensor 120 a) also needs to be reduced sothat pixel cells 605 of image sensor 604 can be positioned close toilluminator 130, to improve the imaging operation (e.g., 3D sensing,stereoscopic imaging) involving illuminator 130 and sensor 120. Byshrinking the footprint of image sensor module 1100, it becomes morelikely to fit image sensor module 1100 into near-eye display 100.

Although the arrangements in FIG. 11A-FIG. 11C, in which holderstructure 1120 forms a stack with image sensor 604, can shrink thefootprint of image sensor module 1100 in a similar way as shown in FIG.8A-FIG. 10, the mounting of the retainer 1124 within housing 1122 cancreate various issues. Those issues can affect the assembly of the imagesensor module as well as the optical properties and performance of theimage sensor module. Specifically, as described above, housing 1122 isbonded to image sensor 604 only via bottom surface 1136, while retainer1124 is not in contact with image sensor 604. But bottom surface 1136 ofhousing 1122 provides a very limited area for applying adhesive 638,which makes the bonding of housing 1122 to image sensor 604 difficult.Moreover, bottom opening 1134 may be enlarged to allow more pixel cells605 of image sensor 604 to receive light, which can improve imagingresolution. But given that housing 1122 surrounds the lens and retainer1124, which increases the footprint, the thickness of housing 1122 needsto be reduced to reduce the footprint. But reducing the thickness ofhousing 1122 reduces bottom surface 1136 of housing 1122 as well as theavailable area for applying adhesive 1138. In one example, as shown inFIG. 11A and FIG. 11C, where the x/y dimension of image sensor 604 isaround 4 millimeter (mm), a minimum width of bottom surface 1136 ofhousing 1122 can be shrunk to about 0.12 mm. The reduced bonding areacan lead to a weaker bonding between housing 1122 and image sensor 604.The weak bonding may allow housing 1122 to shift with respect to imagesensor 604, which changes the orientations and alignment of the lensesstack with respect to image sensor 604 and degrades the light sensingperformance of image sensor module 1100.

Moreover, due to the reduced bonding area, the amount of adhesive 1138applied, as well as the locations on bottom surface 636 where adhesive1138 is applied, need to be controlled with a very high precision. Thisis to prevent the adhesive applied to bottom surface 1136 of housing1122 from spilling into bottom opening 1134 when housing 1122 and imagesensor 604 are brought together. But the requisite precision may becomeunachievable as the area of bottom surface 1136 shrinks to reduce thefootprint of image sensor module 1100. For example, it becomes verydifficult to control the application of adhesive 1138 in an 0.12 mmregion of bottom surface 1136 due to limits imposed by, for example, thediameter of a nozzle that applies the adhesive. The adhesive spilledinto bottom opening 1134 can obfuscate filter 1103 and/or the pixelcells 605 of image sensor 604. All these can degrade the light sensingperformance of the image sensor module.

FIG. 12A, FIG. 12B, and FIG. 12C illustrate examples of an image sensormodule 700 that can address at least some of the issues above. FIG. 12Aillustrates an external side view of image sensor module 1200, whereasFIG. 12B illustrates an internal side view of image sensor module 1200.As shown in FIG. 12A and FIG. 12B, image sensor module 700 includes aholder structure 1120 to hold and physically support one more lenses 602and filter 1103. Holder structure 1220 can be mounted on image sensor604, which in turn is mounted on PCB 720. Holder structure 1220 includesa housing 1222 and a retainer 1224. Housing 1222 can be in the form of abarrel in which one or more lenses 602 are mounted to form a lensesstack, whereas filter 1103 can be mounted on retainer 1224, as in imagesensor module 1100 of FIG. 11A-FIG. 11C. However, unlike in image sensormodule 1100 in which retainer 1124 is mounted within housing 1122 inimage sensor module 1200, at least a part of retainer 1224 is sandwichedbetween housing 1222 and image sensor 604, such that housing 1222,retainer 1224, and image sensor 604 form a stack (e.g., along thez-axis). In addition, retainer 1224 is bonded with image sensor 604 viaan adhesive to set the orientation and position of one or more lenses602 with respect to image sensor 604.

Referring to FIG. 12B, housing 1222, which can be in the form of abarrel, includes a top opening 1232 to receive light and a bottomopening 1234 to output light to image sensor 604. As in image sensormodule 1100, one or more lenses 602 can be loaded into housing 1222 ofimage sensor module 1200 through bottom opening 1234 towards top opening1232. One or more lenses 602 can be mounted at predetermined positionswithin housing 1222 between top opening 1232 and bottom opening 1234 toform a lenses stack, with housing 1222 to provide physical support tothe lenses stack. Housing 1222 further includes a bottom surface 1236which surrounds bottom opening 1234 and can be bonded with a top surface1239 of retainer 1224 via an adhesive layer 740.

FIG. 12C illustrates a magnified internal side view (left diagram) and abottom view (right diagram) of retainer 1224. As shown in FIG. 12C,retainer 1224 includes, in addition to top surface 1239, a middlesurface 1241 and a bottom surface 1242. An outer portion of top surface1239 of retainer 1224 is bonded to bottom surface 1236 of housing 1222via an adhesive 1240, whereas an inner portion of top surface 1239supports one or more lenses 602 to prevent the lenses from falling outof bottom opening 1234 of housing 1222. Moreover, middle surface 1241provides a surface to mount filter 1103. In addition, bottom surface 742of retainer 1224 is flat and is bonded with light receiving surface 610of image sensor 604 via an adhesive 1138. Both adhesives 1138 and 1240can be cured by, for example, UV light to form a bonding layer.

Compared with bottom surface 1136 of housing 1122 of FIG. 11A, the widthof bottom surface 1242 of retainer 1224, as well as the width of bottomsurface 1236 of housing 1222, can be enlarged to increase the bondingarea between retainer 1224 and image sensor 604. In addition, thefootprint of image sensor module 1200 imposes less restriction on thewidth of bottom surface 1242 of retainer 1224. Specifically, referringback to FIG. 11A, bottom surface 1136 of housing 1122 surrounds bothretainer 1124 and filter 1103. As a result, bottom surface 1136 needs tobe made narrower to accommodate the width of retainer 1124 and filter1103 for a given footprint. In contrast, in FIG. 12A-FIG. 12C, bottomsurface 1242 of retainer 1224 may surround filter 1103 only, whereasbottom surface 1236 of housing 1222 only surrounds one or more lenses602. Therefore, even for the same footprint and with the same filter1103, bottom surface 1242 of retainer 1224 of FIG. 12A-FIG. 12C can bemade wider and provide a larger bonding area between retainer 1224 andimage sensor 604, compared with bottom surface 1136 of housing 1122 ofFIG. 11A-FIG. 11C. Moreover, bottom surface 1236 of housing 1222 canalso be made wider and provide a larger bonding area between housing1222 and retainer 1224, compared with the bonding area between housing1122 and retainer 1124 of FIG. 11A-FIG. 11C.

In one example, as shown in FIG. 11C, with a footprint of 4 mm×4 mm(e.g., same as image sensor module 600), the minimum width of bottomsurface 1242 of retainer 1224 is about 0.45 mm, about four times of theminimum width of bottom surface 1136 of housing 1122. In addition, theminimum width of bottom surface 1236 of housing 1222 is about 0.25 mm,about twice of the minimum width of bottom surface 1136 of housing 1122.As a result, an enlarged bonding area can be provided to improve bondingbetween retainer 1224 and image sensor 604, and between housing 1222 andretainer 1224. In addition, with a larger bonding area, the precisionrequirement for application of adhesive 1138 on bottom surface 1242 canalso be relaxed. It also becomes less likely that adhesive 1138 spillsover from bottom surface 742 and obfuscates filter 1103 and/or pixelcells 605 of image sensor 604. All these can improve the performance ofimage sensor module 1200.

Although FIG. 12C illustrates that retainer 1224 includes has arectangular footprint and that filter 1103 has a circular shape, it isunderstood that retainer 1224 and filter 1203 can have other geometricshapes. For example, retainer 1224 can have a cylindrical shape, whereasfilter 1203 can have a rectangular/square shape.

FIG. 13A and FIG. 13B illustrate examples of an image sensor module 1200having additional features to improve bonding between housing 1222 andretainer 1224. The left of FIG. 13A illustrates an external view ofimage sensor module 1200, whereas the right of FIG. 13A illustrates apartial internal view of image sensor module 1200. As shown in FIG. 13A,housing 1222 can include a barrel 1302 as well as a rectangular base1304 which surrounds a part of barrel 1302 and bonds with retainer 1224,whereas barrel 1302 surrounds and holds one or more lenses 602. Housing1222 and retainer 1224 can include complimentary uneven bondingsurfaces. The uneven bonding surfaces increases the total area forapplying adhesive 1240, which can improve the bonding between housing1222 and retainer 1224.

The complimentary uneven bonding surfaces can be provided at variouslocations of housing 1222 and retainer 1224. For example, as shown inFIG. 13A, the bottom of rectangular base 1304 can include a protrusion1306 to provide an uneven bottom surface 1236, whereas the top ofretainer 1224 can include a complimentary notch 1308 to provide anuneven top surface 1239. As another example, as shown in FIG. 8B, top ofretainer 1224 can include, as part of uneven top surface 1239, an outertop surface 1310 and an inner top surface 1312. Outer top surface 1310can have the same rectangular footprint and dimension as bottom surfaceof rectangular base 1304, and bond with the bottom surface ofrectangular base 1304. Moreover, inner top surface 1312 can have thesame rectangular footprint and dimension as the bottom surface of barrel1302, and bond with the bottom surface of barrel 1302. The rectangularfootprint of outer top surface 1310 and rectangular base 1304 canincrease the bonding area and further improve the bonding betweenhousing 1222 and retainer 1224.

The techniques described above in FIG. 11A-FIG. 13B can also be used toreduce the footprint and improve the performance of a light projectormodule, such as illuminator 130 of FIG. 1C. For example, image sensor604 in image sensor modules 1100 and 1200 can be replaced by a lightsource (e.g., an light emitting diode (LED), a laser diode). Lightemitted by the light source can pass through filter 1103 and one or morelenses 602 to form, for example, collimated light beams having a certainfrequency range (e.g., infrared).

FIG. 14A-FIG. 14D illustrates a method 1400 of forming an image sensormodule, such as image sensor modules 900, 1000, 1100, and 1200 of FIG.9A-FIG. 13B, on a PCB 720. Referring to FIG. 14A, method 1400 can startwith step 1402, in which a lens assembly comprising one or more lensesis formed. In some examples, referring to FIG. 14B, lens assembly 902 ofimage sensor module 900 can be formed by first fabricating layers 908and polymer spacers 910 by an injection molding process, in step 1402 a,followed by stacking the layers and spacers to form a lens stack, instep 1402 b, and then followed by coating four sides of the lens stackwith an opaque material to form coating layer 930, in step 1402 c.

In some examples, referring to FIG. 14C, lens assembly 1002 of imagesensor module 1000 can be formed by first fabricating housing 1004,layers 1006, and spacers 1010 (e.g., by an injection molding process),in step 1402 e, followed by inserting the layers 1006 and spacers 1010into housing 1004 to form lens assembly 1002, in step 1402 f. In someexamples, referring to FIG. 11B, one or more lenses 602, which caninclude lens assembly 902, can be loaded into a housing (e.g., housing1122/1222) through a bottom opening of the housing, followed by mountinga retainer either within the housing (e.g., retainer 1124 as in FIG.11A-FIG. 11C) or by mounting a retainer on bottom surfaces of thehousing (e.g., retainer 1224 as in FIG. 12A-FIG. 13B) in step 1402 f,with the retainer providing a surface to attach a filter.

Referring back to FIG. 11A, image sensor 604 can be fabricated, in step1404. The fabrication of image sensor 604 may include fabricating animage sensor die, packaging the image sensor die in a flip-chip package,and depositing solder balls 724 on the flip-chip package. Thefabrication of image sensor 604 further includes forming glass substrate703 on light receiving surface 610 of the image sensor die.

Following step 1404, a reflow process can be performed to conductivelybond image sensor 604 onto PCB 720 to form an image sensor stack, instep 1406. The reflow process can be performed to reflow solder balls724 of the flip-chip packages into a liquid state to form conductivebonds with the contact pads of PCB 720.

Following step 1406, a layer of adhesive can be formed on at least oneof the image sensor stack or the lens assembly. As shown in FIG. 9C, ina case where the adhesive is opaque upon curing, the adhesive can beformed on, for example, a perimeter of glass substrate 703 (of imagesensor 604) around a region 932 facing the light outputting surface ofthe lens assembly. Moreover, in a case where the adhesive isclear/transparent upon curing, the adhesive can be formed in region 932as well to bond glass substrate 703 with the light outputting surface ofthe lens assembly. In some examples, as described with respect to FIG.12A-FIG. 13B, the adhesive (e.g., adhesive 1138) can be formed on abottom surface of the retainer. The adhesive can be cured to form abonding layer in subsequent steps.

Although FIG. 14A illustrates that the fabrication of image sensor 604,the reflow process, and the formation of the adhesive layer in steps1404 to 1408 occur after the formation of the lens assembly in step1402, it is understood that step 1402 can be formed simultaneously orafter any of steps 1404, 1406, or 1408. Referring to FIG. 14D, at theend of step 1408, a lens assembly 900/1000 and/or an image sensor module1100/1200 comprising a holder structure 1120/1220, image sensor 604, andPCB 720 are formed.

In step 1410, the lens assembly and the image sensor stack can bebrought together and connected via the layer of adhesive. In step 1412,at least one of the lens assembly or the image sensor stack can be movedto align the image sensor with the one or more lenses while the imagesensor stack is connected with the lens assembly. Referring back to FIG.9B, the movement of the image sensor stack (and/or the lens assembly)can be based on an alignment process, in which the image sensor can becontrolled to generate sensor data of light received by the image sensorvia the one or more lenses. A degree of alignment between the imagesensor stack and the one or more lenses can be determined based on thesensor data. The position and orientation of the image sensor stack withrespect to the lens assembly can be adjusted until a target degree ofalignment is reached.

In step 1414, with the image sensor stack and the lens assembly at theirrespective aligned position and orientation, a curing process can beperformed to harden the adhesive layer to form bonding layer 904 to bondthe image sensor stack with the lens assembly. The curing process can bebased on ultraviolet light and/or a heat process at a temperature lowerthan the melting point of the one or more lenses.

The techniques described above in FIG. 9A-FIG. 11D can be used to reducethe footprint and improve the performance of a light projector module,such as illuminator 130 of FIG. 1C. For example, image sensor 604 inimage sensor modules 900 and 1000 can be replaced by a light source(e.g., an light emitting diode (LED), a laser diode). Light emitted bythe light source can pass through lens assembly 902 to form, forexample, collimated light beams. The optical properties of the lightbeams (e.g., dispersion, direction) can be affected by the alignment(e.g., based on the relative location and orientation) of lens assembly902 with respect to the light source. Using the techniques describedabove, a light project module with reduced footprint and improvedalignment between lens assembly 902 and the light source, which can leadto improved improvement, can be provided.

Additional Examples

In some examples, an apparatus is provided. The apparatus comprises: alens assembly comprising one or more polymer layers, each layerincluding a lens portion and an extension portion; and an image sensorbelow the lens assembly and bonded to the lens assembly via a bondinglayer and configured to sense light that passes through the lens portionof the one or more polymer layers.

In some aspects, each of the one or more polymer layers is made of acyclic olefin copolymer (COC) material.

In some aspects, each of the one or more polymer layers is made of atleast one of: a polycarbonate material, or a polyester material.

In some aspects, each of the one or more polymer layers is made from oneor more injection molding processes.

In some aspects, a footprint of the lens assembly is substantiallyidentical to a footprint of the image sensor.

In some aspects, the bonding layer is distributed around a perimeter ofthe image sensor to surround a light receiving surface of the imagesensor facing the lens portions of the one or more polymer layers.

In some aspects, the lens assembly further comprises a light outputtingsurface. The bonding layer is distributed over a light receiving surfaceof the image sensor to bond the light receiving surface of the imagesensor with the light outputting surface of the lens assembly.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The extension portion of a pair of polymer layers of theplurality of polymer layers are bonded via an adhesive.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The lens assembly further includes a plurality ofspacers comprising a first spacer, the first spacer being sandwichedbetween the extension portions of a pair of polymer layers of theplurality of polymer layers.

In some aspects, the first spacer is bonded to the extension portions ofthe pair of polymer layers.

In some aspects, the plurality of spacers are made of an opaque materialcomprising one of: a polymer, or a metal.

In some aspects, the one or more polymer layers comprise a plurality ofpolymer layers. The lens portion of a pair of polymer layers of theplurality of polymer layers are bonded via an adhesive.

In some aspects, the apparatus further comprises an opaque coating onexterior surfaces of the lens assembly, wherein the exterior surfaces donot face the image sensor.

In some aspects, the image sensor comprises a substantially flatsubstrate and an integrated circuit die. The light sensed by the imagesensor passes through the substrate. The lens assembly is bonded to thesubstrate.

In some aspects, the apparatus further comprises a printed circuit board(PCB). The image sensor die is conductively bonded to the PCB.

In some aspects, the image sensor is conductively bonded with the PCBvia solder balls by a reflow process.

In some aspects, a temperature of the reflow process is higher than amelting temperature of the one or more polymer layers.

In some aspects, the bonding layer is formed by a curing process at atemperature lower than a temperature of the reflow process to bond theimage sensor to the lens assembly.

In some aspects, the PCB provides mechanical support for the imagesensor. The PCB, the image sensor, and the bonding layer providemechanical support for the lens assembly.

In some aspects, the bonding layer is formed by a curing processinginvolving an ultraviolet light to bond the image sensor to the lensassembly.

In some examples, an apparatus is provided. The apparatus comprises: alens assembly comprising a first layer and a second layer, each of thefirst layer and second layer including a lens portion and an extensionportion, at least of the lens portion or the extension portion of thefirst layer being bonded with, respectively, the lens portion or theextension portion of the second layer to form a lens stack; and an imagesensor below the lens assembly and bonded to the lens assembly via abonding layer and configured to sense light that passes through the lensportions of the first layer and the second layer.

In some aspects, each of the first layer and the second layer is made ofa glass material.

In some examples, an apparatus is provided. The apparatus comprises: alens assembly comprising a first layer, a second layer, and a spacersandwiched between the first layer and the second layer, each of thefirst layer and a second layer including a lens portion and an extensionportion, the extension portions of the first layer and the second layerbeing bonded with the spacer; and an image sensor below the lensassembly and bonded to the lens assembly via a bonding layer andconfigured to sense light that passes through the lens portions of thefirst layer and the second layer.

In some aspects, wherein each of the first layer and the second layer ismade of a glass material.

In some examples, an apparatus is provided. The apparatus comprises: oneor more lenses, an opaque lens holder to hold the one or more lens, andan image sensor below the lens assembly and bonded to the lens assemblyvia a bonding layer, the image sensor configured to sense light thatpasses through the one or more lenses.

In some aspects, the one or more lenses comprise a polymer material.

In some aspects, wherein a footprint of the lens assembly issubstantially identical to a footprint of the image sensor.

In some aspects, the bonding layer is distributed between a perimeter ofthe image sensor and the lens holder.

In some aspects, the lens assembly further comprises a light outputtingsurface surrounded by the lens holder. The bonding layer is distributedover a light receiving surface of the image sensor to bond the lightoutputting surface of the lens assembly with the light receiving surfaceof the image sensor.

In some aspects, the lens holder holds the one or more lenses at one ormore first locations and sets one or more first orientations of the oneor more lenses.

In some aspects, the image sensor is bonded to the lens holder at asecond location and having a second orientation with respect to the lensassembly. The second location and the second orientation of the imagesensor are based on, respectively, the one or more first locations andthe one or more first orientations of the one or more lenses.

In some aspects, the one or more lenses comprise a plurality of lenses.

In some aspects, the lens assembly further comprises a plurality ofspacers, a first spacer of the plurality of spacers being sandwichedbetween a pair of lenses of the plurality of lenses.

In some aspects, the plurality of spacers are made of an opaque materialcomprising one of: a polymer, or a metal.

In some aspects, the opaque lens holder comprises a housing and aretainer. The housing is configured to hold the one or more lenses. Theretainer is configured to retain the one or more lenses within thehousing.

In some aspects, the retainer is positioned within the housing.

In some aspects, at least a part of the retainer is sandwiched betweenthe housing and the image sensor.

In some aspects, the housing includes a top opening to receive the lightand a bottom opening to output the light to the image sensor. The one ormore lenses are mounted at pre-determined positions within the housingbetween the top opening and bottom opening. The housing includes a firstbottom surface surrounding the bottom opening and bonded with a topsurface of the retainer via a first adhesive.

In some aspects, the first bottom surface of the housing is bonded withan outer portion of the top surface of the retainer via the first layerof adhesive. An inner portion of the top surface of the retainer is incontact with the one or more lenses to prevent the one or more lensesfrom falling out of the bottom opening.

In some aspects, the retainer is further configured to hold a filter tofilter the light before the light is detected by the image sensor.

In some aspects, the retainer includes a middle surface to mount thefilter, and a second bottom surface to bond with the image sensor via asecond adhesive.

In some aspects, the filter comprises an array of filters.

In some aspects, the image sensor comprises an image sensor die, and thesecond bottom surface is bonded with the image sensor die via the secondadhesive.

In some aspects, a length and a width of a footprint of the apparatus ona PCB is less than 5 millimeter (mm). A narrowest width of the secondbottom surface of the retainer is longer than 0.4 mm.

In some aspects, the first bottom surface of the housing comprises afirst uneven surface. The top surface of the retainer comprises a seconduneven surface. The first uneven surface and the second uneven surfaceare complimentary to each other and are bonded with each other via thefirst adhesive.

In some aspects, the housing comprises a barrel and a base portion. Thebase portion includes the first uneven surface to bond with the seconduneven surface of the retainer.

In some aspects, the housing comprises a barrel and a base portionsurrounding at least a part of the barrel. The base portion and thebarrel include, respectively, an outer bottom surface and an innerbottom surface as the first uneven surface. The top surface of theretainer includes an outer top surface and an inner top surface as thesecond uneven surface. The outer bottom surface of the base portion isbonded with the outer top surface of the retainer via the firstadhesive. The inner bottom surface of the barrel is bonded with theinner top surface of the retainer via the first adhesive.

In some aspects, the housing and the retainer are made of a polymermaterial using an injection molding process.

In some examples, a method comprises: forming a lens assembly comprisingone or more lenses; performing a reflow process to conductively bond animage sensor onto a printed circuit board (PCB) to form an image sensorstack; forming a layer of adhesive on at least one of the image sensorstack or the lens assembly; connecting the lens assembly and the imagesensor stack via the layer of adhesive; moving at least one of the lensassembly or the image sensor stack to align the image sensor with theone or more lenses; and with the image sensor stack and the lensassembly at their respective aligned positions and orientations, curingthe layer of adhesive to bond the image sensor stack with the lensassembly.

In some aspects, forming the lens assembly comprises fabricating each ofthe one or more lenses using a mold-injection process.

In some aspects, forming the lens assembly comprises enclosing the oneor more lenses in an opaque lens holder to form the lens assembly.

In some aspects, forming the lens assembly comprises loading the one ormore lenses into a housing and attaching a retainer on a bottom surfaceof the housing to prevent the one or more lenses from falling out of thehousing.

In some aspects, the one or more lenses comprise a plurality of lenses.Forming the lens assembly comprises: stacking the plurality of lenseswith a plurality of spacers to form a lens stack, wherein each pair oflens of the plurality of lenses is separated by an opaque spacer of theplurality of spacers in the lens stack; and coating four sides of thelens stack with an opaque material.

In some aspects, the method further comprises: fabricating an imagesensor die; packaging the image sensor die in a flip-chip package;depositing solder balls on the flip-chip package; and bringing theflip-chip packages having the solder balls into contact with contactpads of the PCB. The reflow process is performed to reflow the solderballs of the flip-chip packages into a liquid state to form conductivebonds with the contact pads.

In some aspects, the method further comprises forming a glass substrateon a light receiving surface of the image sensor die.

In some aspects, the layer of adhesive is formed on a perimeter of theglass substrate.

In some aspects, the lens assembly further comprises a light outputtingsurface. The layer of adhesive is distributed on a region of glasssubstrate to bond with the light outputting surface.

In some aspects, moving at least one of the lens assembly or the imagesensor stack to align the image sensor with the one or more lensescomprises: controlling the image sensor to generate sensor data of lightreceived by the image sensor via the one or more lenses; determining adegree of alignment between the image sensor and the one or more lensesbased on the sensor data; and moving at least one of the lens assemblyor the image sensor stack based on the degree of alignment.

In some aspects, curing the layer of adhesive comprises subjecting thelayer of adhesive to ultraviolet light.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the disclosure be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the examples isintended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

What is claimed is:
 1. A method, comprising: forming a lens assemblycomprising one or more lenses; performing a reflow process toconductively bond an image sensor onto a printed circuit board (PCB) toform an image sensor stack; forming a layer of adhesive on at least oneof the image sensor stack or the lens assembly; connecting the lensassembly and the image sensor stack via the layer of adhesive; moving atleast one of the lens assembly or the image sensor stack to align theimage sensor with the one or more lenses; and with the image sensorstack and the lens assembly at their respective aligned positions andorientations, curing the layer of adhesive to bond the image sensorstack with the lens assembly.
 2. The method of claim 1, wherein formingthe lens assembly comprises fabricating each of the one or more lensesusing a mold-injection process.
 3. The method of claim 1, wherein theone or more lenses comprise a plurality of lenses; and wherein formingthe lens assembly comprises: stacking the plurality of lenses with aplurality of spacers to form a lens stack, wherein each pair of lens ofthe plurality of lenses is separated by a spacer of the plurality ofspacers in the lens stack.
 4. The method of claim 3, wherein theplurality of spacers are formed using a mold-injection process.
 5. Themethod of claim 3, further comprising coating four sides of the lensstack with an opaque material.
 6. The method of claim 3, wherein theplurality of spacers are made of an opaque material comprising one of: apolymer or a metal.
 7. The method of claim 1, further comprising:fabricating an image sensor die; packaging the image sensor die in aflip-chip package; depositing solder balls on the flip-chip package; andbringing the flip-chip packages having the solder balls into contactwith contact pads of the PCB, wherein the reflow process is performed toreflow the solder balls of the flip-chip packages into a liquid state toform conductive bonds with the contact pads.
 8. The method of claim 7,further comprising: forming a glass substrate on a light receivingsurface of the image sensor die.
 9. The method of claim 8, wherein thelayer of adhesive is formed on a perimeter of the glass substrate. 10.The method of claim 8, wherein the lens assembly further comprises alight outputting surface; and wherein the layer of adhesive isdistributed on a region of glass substrate to bond with the lightoutputting surface.
 11. The method of claim 1, wherein moving at leastone of the lens assembly or the image sensor stack to align the imagesensor with the one or more lenses comprises: controlling the imagesensor to generate sensor data of light received by the image sensor viathe one or more lenses; determining a degree of alignment between theimage sensor and the one or more lenses based on the sensor data; andmoving at least one of the lens assembly or the image sensor stack basedon the degree of alignment.
 12. The method of claim 11, wherein afootprint of the lens assembly is substantially identical to a footprintof the image sensor.
 13. The method of claim 1, wherein the curing thelayer of adhesive comprises subjecting the layer of adhesive toultra-violet light.
 14. The method of claim 1, wherein the curing thelayer of adhesive comprises subjecting the layer of adhesive to a heatprocess at a temperature lower than the melting point of the one or morelenses.
 15. The method of claim 1, wherein the adhesive is opaque or hasa low light transmittance upon hardening by the curing of the adhesive.16. The method of claim 1, further comprising fabricating a housing tohold the one or more lenses.
 17. The method of claim 16, wherein the oneor more lenses comprise a plurality of lenses; and wherein forming thelens assembly comprises: stacking the plurality of lenses with aplurality of spacers to form a lens stack, wherein each pair of lens ofthe plurality of lenses is separated by a spacer of the plurality ofspacers in the lens stack; and inserting the lens stack into the housingto form the lens assembly.
 18. The method of claim 17, furthercomprising mounting a retainer to the housing to secure the lensassembly, wherein the image sensor is bonded to either the housing orthe retainer.
 19. The method of claim 1, wherein the one or more lensescomprise a polymer material.
 20. The method of claim 19, wherein thepolymer material comprises a cyclo olefin copolymer (COC) material.